Novel demulsifiers

ABSTRACT

The invention relates to novel demulsifiers for use in the demulsification of oils from water and vice versa, including the demulsification of crude oil from sea water or brine. In particular, the present invention relates to novel demulsifiers which are environmentally friendly, or ‘green’, and which can be used without restriction on-site in offshore oil drilling fields, for example in the North Sea. The novel demulsifiers are based on the reaction product of alkoxylated polyols or polyol esters with dicarboxylic acids.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase application of PCTInternational Application No. PCT/GB2012/052340, filed Sep. 21, 2012,and claims priority of British Patent Application No. 1116419.1, filedSep. 23, 2011, the disclosures of which are incorporated herein byreference in their entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates to novel demulsifiers for use in thedemulsification of oils, including crude oil. In particular, the presentinvention relates to novel demulsifiers which are environmentallyfriendly, or ‘green’, and which can be used without restriction on-sitein offshore oil drilling fields, for example in the North Sea. The noveldemulsifiers are based on alkoxylated sorbitol or sorbitan esters withdicarboxylic acid.

BACKGROUND OF THE INVENTION

Demulsifiers, or emulsion breakers, are chemicals which are used toseparate salted water from crude oil emulsions. They are used in theprocessing of crude oil which is typically recovered along withsignificant quantities of brine, usually in the form of sea/ocean water.It is important to remove the brine from the crude oil as quickly aspossible to allow dry oil to be stored and shipped as necessary, and toallow ‘clean’ brine, i.e. brine containing no oil, to be discharged.

Common demulsifiers are generally polymeric surfactants such ascopolymers of polyoxyethylene and polypropylene oralkylphenol-formaldehyde resins and/or blends of various surface activesubstances.

Demulsifiers, like those of the type described above, are containedwithin the ‘clean’ brine after demulsification. The easiest and mostcost effective way of discharging the ‘clean’ brine from the crude oilstream is by pumping it back into the sea/ocean onsite. Therefore, thedemulsifiers present in the ‘clean’ brine are also discharged back intothe sea/ocean with the brine.

Demulsifiers of the types described above comprise phenol groups, and assuch are not environmentally friendly. The discharging of thesedemulsifiers into the sea increases the levels of phenol groups presentin the sea and thus harms marine life present in the area.

In the oilfield industry, there is a move towards more environmentallyacceptable chemicals that are less hazardous than the standardproduction chemicals described above. For example, drilling sites in theNorth Sea are regulated by the rules of the Convention for theProtection of the Marine Environment of the North-East Atlantic (OSPAR).These rules restrict the toxicity of allowed demulsifiers and placestringent values on the biodegradability and the like of all chemicalsto be used in the marine environment. However, it has been generallyfound that the more environmentally acceptable demulsifiers do not havethe same level of efficacy as the standard production chemicals.

There is, therefore, a need for a demulsifier which shows the same orsuperior properties and efficacy as the standard production chemicals,but which is environmentally friendly and reaches or surpasses the rulesof the OSPAR.

It is an object of the present invention to address at least one of theabove or other disadvantages associated with the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda novel demulsifier comprising the reaction product of:

-   -   a) an alkoxylated polyol or ester thereof; and    -   b) a dicarboxylic acid.

According to a second aspect of the present invention, there is provideda novel demulsifier obtainable by reacting:

-   -   a) an alkoxylated polyol or ester thereof; and    -   b) a dicarboxylic acid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to at least one embodiment of the present invention, ademulsifier comprises the reaction product of:

-   -   a) an alkoxylated polyol or ester thereof; and    -   b) a dicarboxylic acid.

In accordance with at least one emdodiment, the demulsifier isobtainable by reacting:

-   -   a) an alkoxylated polyol or ester thereof; and    -   b) a dicarboxylic acid.

When used herein, the term “dicarboxylic” refers to an acid comprisingtwo functional groups, i.e. carboxylate groups. The term dicarboxylicacid defines the group of compounds containing both bi-functionalcarboxylic acids and dimer acids.

The demulsifier is operable to separate oil-in-water and/or water-in-oilemulsions. Preferably, the demulsifier is operable to separatewater-in-oil emulsions of the type commonly harvested in crude oildrilling. Preferably, the demulsifier is operable to separate brine fromcrude oil.

The polyol in the alkoxylated species preferably comprises at least 3hydroxyl groups. Preferably, the polyol in the alkoxylated speciescomprises up to 9 hydroxyl groups. Desirably, the polyol has an averageof 1 or 2 primary hydroxyl groups and at least 1, preferably 1 to 4secondary hydroxyl groups.

Preferably, the polyol in the alkoxylated species has the formula (I):

R¹—(OH)_(n)   (I)

where n is from 3 to 8 and particularly from 3 to 6.

The group R¹ is desirably an aliphatic hydrocarbyl group. Preferably,the group R¹ is saturated. Preferably, R¹ has from 3 to 10 carbon atoms,preferably from 3 to 8, and especially from 3 to 6 carbon atoms. R¹ willusually be linear, though it may include branching.

Desirably, the polyol in the alkoxylated species has the general formula(la):

HOH₂C—(CHOH)_(p)—CH₂OH   (Ia)

where p is from 1 to 6, more preferably from 1 to 4.

Suitable polyols include glycerol, C₄ polyols such as threitol anderythritol, C₅ polyols such as inositol, arabitol and xylitol and C₆polyols such as sorbitol, and compounds derived therefrom, for examplesorbitan. The C₄ to C₆ polyols are commonly the reduced or hydrogenatedforms of corresponding tetrose, pentose and hexose sugars. Desirably thepolyol is glycerol or a derivative thereof, particularly sorbitol orsorbitan (usually derived in situ from sorbitol) or a mixture orcombination of these.

The polyol may be present in the demulsifier in an esterified form.Preferably, when the polyol is sorbitan, the sorbitan is present in thedemulsifier in the form of an ester derived from the reaction of thesorbitan with a fatty acid or derivative thereof.

Preferred fatty acids or derivatives thereof comprise in the range from6 to 24, more preferably 8 to 20, particularly 10 to 18, and especially12 to 16 carbon atoms. Linear fatty acids are preferred. Suitable fattyacids include capric, lauric, myristic, palmitic, stearic, and/orbehenic acid.

Suitable fatty acids or derivatives thereof for reaction with thesorbitol or derivative thereof are preferably derived from naturalsources, preferably from vegetable sources. For example, lauric acid isthe main acid in coconut oil and in palm kernel oil. It may also befound in animal milk, for example cow's milk and goat's milk. The fattyacids or derivatives thereof may be derived from palm oil, American oilpalm oil, nutmeg oil, peach palm seed oil, betel nut, date seed,macadamia nut oil, watermelon seed oil, pumpkin seed or flower oil, andother vegetable sources.

In one embodiment, the polyol or ester thereof is a sorbitan compound,more specifically, a sorbitan ester. Suitable sorbitan esters includesorbitan cocoate, sorbitan caprate, sorbitan laurate, sorbitanmyristate, sorbitan palmitate and/or sorbitan stearate. Preferredsorbitan esters are sorbitan caprate and/or sorbitan laurate, preferablysorbitan monolaurate.

The polyol present in the demulsifier is alkoxylated. The alkoxylatedpolyol preferably comprises residues of an alkoxy group, preferably aunivalent radical R²—O—, or anion R²—O⁻, where R² is an alkyl group,preferably a C₁ to C₆ alkyl group, preferably C₁ to C₄ and morepreferably C₂ to C₃.

Preferably, the alkoxy group is a methoxy group, ethoxy group or propoxygroup, preferably ethoxy or propoxy. An increase in the presence ofethoxy groups in the alkoxylated polyol or ester thereof increases thesolubility of the demulsifier in water, or in aqueous phases ofoil-in-water and/or water-in-oil emulsions. An increase in the presenceof propoxy groups in the alkoxylated polyol or ester thereof decreasesthe solubility of the demulsifier in water, or in aqueous phases ofoil-in-water and/or water-in-oil emulsions.

The presence of ethoxy groups in the alkoxylated species increases thehydrophilic-lipophillic balance (HLB) of the alkoxylated species. Thepresence of propoxy groups in the alkoxylated species lowers the HLB ofthe alkoxylated species.

Preferably, ethoxy groups are present in the alkoxylated polyol or esterthereof at a pre-determined concentration to provide the desired watersolubility and/or HLB in the demulsifier. Alternatively, a mixture ofethoxy and propoxy groups may be present to provide the desired watersolubility and/or HLB in the demulsifier.

Preferably, the alkoxylated polyol or ester thereof is derived from thereaction of an alkylene oxide with the polyol or ester thereof. One ormore equivalents of alkylene oxide may react with each polyol moleculeor molecule of the ester thereof. Preferably, the polyol ispolyalkoxylated. Preferably, the alkylene oxide is selected from thegroup comprising C₁ to C₆ alkylene oxides, preferably C₁ to C₄ and morepreferably C₂ to C₃ alkylene oxides. Preferably, the alkylene oxide isethylene oxide or propylene oxide or a mixture thereof.

Preferably, the alkoxylated polyol or ester thereof comprises between 1and 500 alkylene oxide equivalents per molecule, preferably between 1and 400, more preferably between 1 and 200 and most preferably between 2and 100 alkylene oxide equivalents per molecule.

Where the number of equivalents of alkylene oxide is given in terms ofper molecule, preferably, this is the average number of equivalents permolecule in a sample of the product. Individual molecules in the samplemay have fewer or greater than the stated number of equivalents ofalkylene oxide, but on average, the sample will comprise moleculeshaving an average of the stated number of equivalents of alkylene oxide.

Where the demulsifier comprises an alkoxylated polyol, there arepreferably between 1 and 500 alkylene oxide equivalents per molecule,preferably between 2 and 400, more preferably between 5 and 200 and mostpreferably between 10 and 100 alkylene oxide equivalents per polyolmolecule.

Where the demulsifier comprises an alkoxylated ester of a polyol, thereare preferably between 1 and 500 alkylene oxide equivalents permolecule, preferably between 2 and 300, more preferably between 3 and150 and most preferably between 5 and 50 alkylene oxide equivalents permolecule.

In one embodiment, the alkoxylated polyol is preferably an alkoxylatedsorbitol, more preferably an ethoxylated sorbitol. Preferably, thealkoxylated polyol comprises between 1 and 500 alkylene oxideequivalents per molecule, preferably between 1 and 400, more preferablybetween 1 and 200 and most preferably between 2 and 100 alkylene oxideequivalents per sorbitol molecule. Preferably, the alkoxylated sorbitolhas the general structure (II):

where a,b,c,d,e and f may each independently be any number between 0 and100; AO is an alkylene oxide residue, preferably an ethylene oxide (EO)residue; and where a+b+c+d+e+f is between 1 and 500, preferably between1 and 400, more preferably between 1 and 200, even more preferablybetween 2 and 100 and most preferably between 10 and 40.

Preferably, in this embodiment, the alkoxylated polyol is an ethoxylatedsorbitol, more preferably a polyoxyethylene (X) sorbitol, wherein X is anumber between 1 and 40, preferably polyoxyethylene (10) sorbitol orpolyoxyethylene (40) sorbitol, where a+b+c+d+e+f in formula (II) is 10or 40, most preferably polyoxyethylene (40) sorbitol, where a+b+c+d+e+fin formula (II) is 40. Polyoxyethylene (40) sorbitol is availablecommercially from Croda under the trade name Atlas^(TM) G2004.

In another embodiment, the alkoxylated polyol ester is preferably analkoxylated sorbitan ester, more preferably an ethoxylated sorbitanester. Preferably, the alkoxylated polyol ester comprises between 1 and500 alkylene oxide equivalents per molecule, preferably between 1 and400, more preferably between 1 and 200 and most preferably between 2 and100 alkylene oxide equivalents per sorbitan ester molecule. Preferably,the alkoxylated sorbitan ester has the general structure (III):

where w,x,y and z may each independently be any number between 0 and100; AO is an alkylene oxide residue, preferably an ethylene oxide (EO)residue; R is an alkyl group; andwhere w+x+y+z is between 1 and 300, preferably between 2 and 200, morepreferably between 3 and 100 and most preferably between 5 and 50.

In formula (III), R may be saturated or unsaturated, preferablysaturated. R preferably comprises between 1 and 29 carbon atoms,preferably between 5 and 25, preferably between 9 and 21, morepreferably between 11 and 17. Preferably R is derived from a fatty acid,preferably selected from the group comprising lauric acid, palmiticacid, stearic acid and oleic acid.

Preferably, in this embodiment, the alkoxylated polyol ester is anethoxylated sorbitan ester, preferably an ethoxylated sorbitanmonolaurate, monopalmitate, monostearate or monooleate, more preferablyan ethoxylated sorbitan monolaurate, and most preferably polyoxyethylene(20) sorbitan monolaurate, where w+x+y+z in formula (III) is 20.Polyoxyethylene (20) sorbitan monolaurate is available commercially fromCroda under the trade name Tween™ 20.

The dicarboxylic acid present in the demulsifier preferably has from 4to 40 carbon atoms. Preferably, the dicarboxylic acid is aliphatic.Typically, the dicarboxylic acid is of the formula (IV):

HOOC—R³—COOH   (IV)

where R³ is a C₂ to C₃₆ hydrocarbyl group which can be saturated orunsaturated, linear or branched and can be aromatic e.g. a phenyl ring(thus giving a phthalic, terephthalic or iso-phthalic dicarboxylic acid)or, desirably, aliphatic e.g. an alkylene or alkenylene group, and maybe cyclic though it is desirably open chain. Commonly R³ R is a group:—(CH₂)_(m)-, where m is from 2 to 36. Suitable reactive derivatives ofthe dicarboxylic acids include lower e.g. C₁ to C₄ and particularlymethyl, alkyl esters (usually diesters) and anhydrides, particularlycyclic anhydrides such as succinic, maleic and phthalic anhydrides.

In one embodiment, the dicarboxylic acid has at least 4 carbon atoms,preferably at least 5 and more preferably at least 6 carbon atoms. Inthis embodiment, the dicarboxylic acid preferably comprises up to 36carbon atoms, preferably up to 20 carbon atoms, more preferably up to 12carbon atoms and most preferably up to 10 carbon atoms. In thisembodiment, the dicarboxylic acid may be selected from the groupcomprising malonic acid, succinic acid, glutaric acid, adipic acid,pimelic acid, suberic acid, axelaic acid and sebacic acid, preferablyadipic acid, suberic acid and sebacic acid, more preferably adipic acid.

In another embodiment, the dicarboxylic acid is preferably a dimer acid.In this embodiment, the dimer acid preferably comprises from 24 to 52carbon atoms, preferably from 28 to 48 carbon atoms, more preferablyfrom 32 to 46 carbon atoms and most preferably from 36 to 44 carbonatoms. Preferably the dimer acid is a C36 dimer acid.

The term dimer fatty acid is well known in the art and refers to thedimerisation product of mono- or polyunsaturated fatty acids and/oresters thereof. Preferred dimer acids are dimers of C₁₀ to C₃₀, morepreferably C₁₂ to C₂₄, particularly C_(u) to C₂₂, and especially C₁₈alkyl chains. Suitable dimer fatty acids include the dimerisationproducts of oleic acid, linoleic acid, linolenic acid, palmitoleic acid,and elaidic acid. The dimerisation products of the unsaturated fattyacid mixtures obtained in the hydrolysis of natural fats and oils, e.g.sunflower oil, soybean oil, olive oil, rapeseed oil, cottonseed oil andtall oil, may also be used. Hydrogenated, for example by using a nickelcatalyst, dimer fatty acids may also be employed.

In addition to the dimer fatty acids, dimerisation usually results invarying amounts of oligomeric fatty acids (so-called “trimer”) andresidues of monomeric fatty acids (so-called “monomer”), or estersthereof, being present. The amount of monomer can, for example, bereduced by distillation. Particularly preferred dimer fatty acids have adicarboxylic (or dimer) content of greater than 70%, more preferablygreater than 85%, and particularly greater than 94% by weight.

Preferably, the molar ratio of alkoxylated polyol or ester thereof todicarboxylic acid in the reaction product is at least 0.05:1, preferablyat least 0.1:1, more preferably at least 0.5:1 and most preferably atleast 1:1. Preferably, the molar ratio of alkoxylated polyol or esterthereof to dicarboxylic acid in the reaction product is up to 20:1,preferably up to 10:1, more preferably up to 5:1 and most preferably upto 3:1.

Optionally, the reaction product of the alkoxylated polyol or esterthereof and the dicarboxylic acid may further comprise an end-cap.Preferably, the end-cap comprises a monovalent radical. Preferably, theend-cap comprises a monocarboxylic acid.

Preferably, the monocarboxylic acid is a fatty acid. Preferably, themonocarboxylic acid comprises from 2 to 30 carbon atoms preferablybetween 12 and 26, more preferably between 14 and 22 carbon atoms andmost preferably between 18 and 22 carbon atoms. The monocarboxylic acidmay be selected from the group comprising lauric acid, myristic acid,palmitic acid, stearic acid, arachidic acid and behenic acid, preferablystearic acid and behenic acid.

Fatty acids suitable for use herein can be obtained from natural sourcessuch as, for example plant or animal esters. For example, the acids maybe obtained from palm oil, rape seed oil, palm kernel oil, coconut oil,babassu oil, soybean oil, castor oil, sunflower oil, olive oil, linseedoil, cottonseed oil, safflower oil, tallow, whale or fish oils, grease,lard and mixtures thereof. The fatty acids can also be syntheticallyprepared. Relatively pure unsaturated fatty acids such as oleic acid,linoleic acid, linolenic acid, palmitoleic acid, and elaidic acid may beisolated, or relatively crude unsaturated fatty acid mixtures employed.Resin acids, such as those present in tall oil, may also be used.

Preferably, the monocarboxylic acid is saturated. The fatty acid may beeither a branched fatty acid or a linear fatty acid. A mixture of fattyacids may be present. In this case, the mixture may comprise branchedfatty acids, linear fatty acids, or a mixture thereof.

Preferably, the molar ratio of the end-cap to the reaction product ofthe alkoxylated polyol or ester thereof and the dicarboxylic acid is atleast 0.05:1, preferably at least 0.1:1, more preferably at least 0.2:1and most preferably at least 0.35:1. Preferably, molar ratio of theend-cap to the reaction product of the alkoxylated polyol or esterthereof and the dicarboxylic acid is up to 20:1, preferably up to 10:1,more preferably up to 5:1 and most preferably up to 2:1.

Preferably, the molar ratio of the alkoxylated polyol or ester thereofto the dicarboxylic acid to the end-cap is at least 1:0.1:1 and morepreferably at least 1:0.5:1. Preferably, molar ratio of the end-cap tothe reaction product of the alkoxylated polyol or ester thereof and thedicarboxylic acid is up to 1:1:5 and more preferably up to 1:1:2.

Preferably, the reaction product has a molecular weight of greater than700 Daltons, preferably greater than 1000 Daltons, more preferablygreater than 1500 Daltons and most preferably greater than 2000 Daltons.Preferably, the reaction product has a molecular weight of less than100000 Daltons, preferably less than 80000 Daltons, more preferably lessthan 50000 Daltons and most preferably less than 20000 Daltons.

Preferably, the reaction product has a relative solubility number (RSN)of at least 2, preferably at least 4, more preferably at least 6 andmost preferably at least 8. Preferably, the reaction product has an RSNof up to 100, preferably up to 60, more preferably up to 30 and mostpreferably up to 20. The RSN is a measure of the solubility of thedemulsifier and corresponds to the hydrophilic-lipophilic balance of thedemulsifier. The RSN can be determined according to the method set outin Wu et al, Colloids and surfaces: A, Physicochemical and engineeringaspects; 2004; Vol. 232(2-3); pages 229-237.

Preferably, the reaction product has a toxicity of less than 20,000mg/l,preferably less than 15,000 mg/l, preferably less than 10,000 mg/l andmost preferably less than 5,500mg/l. The toxicity is determinedaccording to the method set out below in Experimental Example 2.

Preferably, the reaction product shows a biodegradation of at least 1%,preferably at least 5%, more preferably at least 8% and most preferablyat least 10%. The biodegradation is determined according to the methodset out below in Experimental Example 2

Preferably, the reaction product has a viscosity at 25° C. of greaterthan 100 mPa·s, preferably greater than 300 mPa·s, more preferablygreater than 500 mPa·s and most preferably greater than 900 mPa·s. Theviscosity is measured at 25° C. on a Brookfield viscometer using a 29Spindle at a shear rate of 0.25N.

Preferably, the reaction product has a pour point of less than 100° C.,preferably less than 80° C., more preferably less than 50° C. and mostpreferably less than 30° C.

Preferably, the reaction product has a pour point of greater than 1° C.,preferably greater than 5° C., more preferably greater than 10° C.Preferably, the pour point is measured on an ISL MPP 5Gs automated pourpoint analyser according to the ASTM D97 standard method.

Preferably, the reaction product has a pH which is approximatelyneutral. Preferably, the reaction product has a pH of between 3 and 12,preferably between 4 and 10, more preferably between 5 and 8 and mostpreferably between 6 and 7. The pH of the reaction product is measuredat a concentration of 1% in an 85% IPA solution using an HI 8424portable pH probe.

Preferably, the reaction product has a density at 25° C. of at least 0.1g/cm³, preferably at least 0.5 g/cm³, more preferably at least 0.8g/cm³, and most preferably at least 1.0 g/cm³. Preferably, the reactionproduct has a density at 25° C. of up to 10 g/cm³, preferably up to 5g/cm³, more preferably up to 3 g/cm³, and most preferably up to 2 g/cm³.The density may be determined by pouring 10 ml of sample into ameasuring cylinder and calculating the approximate density from theweight.

Preferably, the reaction product has good thermal stability in airand/or nitrogen. Preferably, the reaction product is stable in air up toa temperature of at least 50° C., preferably at least 100° C., morepreferably at least 150° C. and most preferably at least 200° C. beforethe product starts to degrade. Preferably, the reaction product isstable in nitrogen up to a temperature of at least 50° C., preferably atleast 100° C., more preferably at least 150° C. and most preferably atleast 200° C. before the product starts to degrade. The thermalstability in air and nitrogen was measured according to the method setout in Experimental Example 1 below.

Preferably, the reaction product shows a mass loss in air over a periodof 1 hour at 150° C. of less than 50%, preferably less than 30%, morepreferably less than 15% and most preferably of less than 7%.Preferably, the reaction product shows a mass loss in air over a periodof 1 hour at 200° C. of less than 90%, preferably less than 85%, morepreferably less than 80% and most preferably of less than 75%. The massloss was measured according to the method set out in ExperimentalExample 1 below.

Preferably, the demulsifier is used at a dosage rate of between 0.01 and1000 ppm, preferably between 0.05 and 800 ppm, more preferably between0.1 and 500 ppm and most preferably between 0.5 and 100 ppm in theemulsion to be demulsified.

It should be noted that particular demulsifiers can be extremelyemulsion-specific. Therefore, the failure of a demulsifier to work onone or two tests does not mean that the demulsifier is unsuitableeverywhere. This fact makes it extremely difficult to judge the worth ofa particular potential demulsifier based on a few negative resultsalone. Positive results, however, may point to the worth not only of thedemulsifier itself, but of the class of chemistry that that particulardemulsifier represents. Consequently, the existence of several cases ofoutstanding positive performance gives credibility to this invention asa whole.

According to a second aspect of the present invention, there is provideda demulsification formulation comprising a demulsifier which is thereaction product of:

-   -   a) an alkoxylated sorbitol or sorbitan ester;    -   b) a dicarboxylic acid; and    -   c) optionally, an end-cap.

Preferably, the demulsification formulation is for demulsifying anoil-in-water or a water-in-oil emulsion.

Preferably, the demulsifier which is the reaction product of thealkoxylated polyol or ester thereof, dicarboxylic acid and optionalend-cap is present in the demulsification formulation at a concentrationof at least 2% w/w based on the total weight of the demulsificationformulation, preferably at least 5% w/w, more preferably at least 10%w/w and most preferably at least 15% w/w. Preferably, the demulsifier ispresent in the demulsification formulation at a concentration of up to80% w/w based on the total weight of the demulsification formulation,preferably up to 60% w/w, more preferably up to 50% w/w and mostpreferably up to 30% w/w.

Preferably, the demulsification formulation also comprises a solvent.The solvent is preferably a derivative of the oil phase of the emulsionto be demulsified. For example, for crude oil, the solvent may beselected from xylene, heavy or light aromatic naphtha, IPA, methanol2EH, diesel or toluene.

Preferably, the solvent is present in the demulsification formulation ata concentration of at least 20% w/w based on the total weight of thedemulsification formulation, preferably at least 30% w/w, morepreferably at least 40% w/w and most preferably at least 50% w/w.Preferably, the solvent is present in the demulsification formulation ata concentration of up to 98% w/w based on the total weight of thedemulsification formulation, preferably up to 90% w/w, more preferablyup to 80% w/w and most preferably up to 70% w/w.

Preferably, the solvent is present in the demulsification formulation ata ratio to the demulsifier of up to 50:1, preferably up to 30:1, morepreferably up to 20:1 and most preferably up to 10:1. Preferably, thesolvent is present in the demulsification formulation at a ratio to thedemulsifier of at least 1:10, preferably at least 1:5, more preferablyat least 1:2 and most preferably at least 1:1.

The demulsification formulation may optionally further comprise awetting agent. Preferably, the wetting agent is a surfactant, preferablyan anionic surfactant. Preferably, the wetting agent is or comprises anester. Any suitable surfactant, particularly an ester-containingsurfactant, or mixtures thereof may be used as the wetting agent in thepresent invention. Examples of suitable wetting agents include, but arenot limited to alkyl sulfates, such as ammonium lauryl sulfate, sodiumlauryl sulfate; alkyl ether sulfates, such as sodium laureth sulfate,also known as sodium lauryl ether sulfate (SLES), sodium myreth sulfate;sulfonates such as dioctyl sodium sulfosuccinate,perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate; alkyl benzenesulfonates; phosphates such as alkyl aryl ether phosphate, akyl etherphosphate, carboxylates such as alkyl carboxylates, i.e. Fatty acidsalts (soaps), sodium stearate, Sodium lauroyl sarcosinate, carboxylatefluorosurfactants (perfluorononanoate, perfluorooctanoate (PFOA or PFO))and Synperonic™ LF/30 (ex Croda).

When present, the wetting agent is preferably present in thedemulsification formulation at a concentration of at least 1% w/w basedon the total weight of the demulsification formulation, preferably atleast 3% w/w, more preferably at least 6% w/w and most preferably atleast 8% w/w. Preferably, when present, the wetting agent is present inthe demulsification formulation at a concentration of up to 25% w/wbased on the total weight of the demulsification formulation, preferablyup to 20% w/w, more preferably up to 15% w/w and most preferably up to12% w/w.

The demulsification formulation may optionally further comprise analkylene oxide block copolymer, for example an ethylene oxide(EO)/propylene oxide (PO) block copolymer. The block copolymer may beeither an EO-P0 copolymer, EO-PO-EO copolymer or PO-EO-PO copolymer.Preferably, the block copolymer has a molecular weight of betweenapproximately 1000 and 10000, preferably between 1500 and 8000, morepreferably between 2000 and 7000. Preferably, the block copolymer has anHLB of between 0.1 and 20, preferably between 0.5 and 17, and orepreferably between 1 and 15. Examples of suitable block copolymersinclude, but are not limited to Surfonic™ EO/PO block copolymers exHuntsman and EO/PO block copolymers from Ineos Oxide.

When present, the alkylene oxide block copolymer is preferably presentin the demulsification formulation at a concentration of at least 1% w/wbased on the total weight of the demulsification formulation, preferablyat least 3% w/w, more preferably at least 6% w/w and most preferably atleast 8% w/w. Preferably, when present, the alkylene oxide blockcopolymer is present in the demulsification formulation at aconcentration of up to 25% w/w based on the total weight of thedemulsification formulation, preferably up to 20% w/w, more preferablyup to 15% w/w and most preferably up to 12% w/w.

Preferably, the demulsification formulation is anhydrous. Preferably,the demulsification formulation comprises less than 5% water, preferablyless than 3%, more preferably less than 2% and most preferably less than1% water.

It will be appreciated that the exact composition of demulsifyingformulations will vary according to the particular emulsion it is to beused on, and even for crude oil obtained from the same well, over time,the optimum amount of demulsifier will vary as the production conditionschange. For example, different temperature and pressure conditions,concentrations of naturally occurring emulsifiers, productiontechniques, etc., make it impossible to predict in advance thedemulsifier proportions required.

Preferably, the demulsification formulation is used at a dosage rate ofbetween 1 and 1000 ppm, preferably between 5 and 800 ppm, morepreferably between 15 and 500 ppm and most preferably between 20 and 200ppm in the emulsion to be demulsified.

According to a third aspect of the present invention, there is provideda method of demulsifying an oil-in-water or water-in-oil emulsion, themethod comprising adding a reaction product of:

-   -   a) an alkoxylated sorbitol or sorbitan ester;    -   b) a dicarboxylic acid; and    -   c) optionally, an end-cap to the emulsion.

Preferably, the emulsion is a water-in-oil emulsion. Preferably, theemulsion is an emulsion of water, preferably salted water, morepreferably sea/ocean water in crude oil.

According to a further aspect of the invention, there is provided theuse of a reaction product of:

-   -   a) an alkoxylated sorbitol or sorbitan ester;    -   b) a dicarboxylic acid; and    -   c) optionally, an end-cap        as a demulsifier.

Preferably, the reaction product is used in the demulsification of anoil-in-water or water-in-oil emulsion, preferably a crude oil emulsion.

Any of the above features of the invention may be combined in anycombination and with any aspect of the invention.

EXAMPLES

The present invention will now be described further, for illustrativepurposes only, in the following examples. All parts and percentages aregiven by weight unless otherwise stated.

Preparation Process

Demulsifier

A composition comprising sorbitan (20EO) monolaurate and adipic acid ina 2:1 molar ratio was produced.

384 kg of sorbitan (20EO) monolaurate was added to the reaction vesseland heated to 80° C. whilst stirring. 23 kg of adipic acid flake wasslowly added to the warm stirred sorbitan (20EO) monolaurate. Themixture was heated to 235° C. observing distillation water removal. Thereaction was continued until an acid value of the less than 5 mgKOH/gwas observed.

The reaction yielded 400 kg of reaction product and 5.8 kg water.

Demulsifier 2

A composition comprising sorbitan (20EO) monolaurate, adipic acid andstearic acid in a 2:1:2 molar ratio was produced.

313 kg of sorbitan (20EO) monolaurate was added to the reaction vesseland heated to 60° C. whilst stirring. 73 kg of stearic acid flake wasslowly added to the warm stirred sorbitan (20EO) monolaurate and theresulting mixture heated to 80° C. 19 kg of adipic acid flake was thenadded to the mixture in the reaction vessel. The mixture was heated to235° C. observing distillation water removal. The reaction was continueduntil an acid value of the less than 5 mgKOH/g was observed.

The reaction yielded 400 kg of reaction product and 4.8 kg water.

Demulsifier 3

A composition comprising sorbitol (40EO), adipic acid and stearic acidin a 1:1:2 molar ratio was produced.

299 kg of sorbitol (40EO) was added to the reaction vessel and heated to60° C. whilst stirring. 86 kg of stearic acid flake was slowly added tothe warm stirred sorbitol (40EO) and the resulting mixture heated to 80°C. 23 kg of adipic acid flake was then added to the mixture in thereaction vessel. The mixture was heated to 235° C. observingdistillation water removal. The reaction was continued until an acidvalue of the less than 5mgKOH/g was observed.

The reaction yielded 400 kg of reaction product and 8.3 kg water.

Demulsifier 4

A composition comprising sorbitol (40EO) and C₃₆ dimer acid in a 4:3molar ratio was produced.

72 kg of C₃₆ dimer acid was added to the reaction vessel and heated to80° C. whilst stirring. 335 kg of sorbitol (40EO) was slowly added tothe warm stirred C₃₆ dimer acid. The mixture was heated to 235° C.observing distillation water removal. The reaction was continued untilan acid value of the less than 5mgKOH/g was observed

The reaction yielded 400 kg of reaction product and 5 kg water.

Formulation 1

A formulation was prepared comprising the following:

Demulsifier 1 20% EO/PO block polymer (Surfonic ™ block copolymer, 10%ex Huntsman) Ester/wetting agent (ethylene oxide/propylene oxidecopolymer, 10% based on a C13/C15 alcohol, for example Synperonic ™LF/30, ex Croda) Solvent (diesel) 60%

Formulation 2

A formulation was prepared comprising the following:

Demulsifier 3 30% EO/PO block polymer (Surfonic ™ block copolymer, 12%ex Huntsman) Ester/wetting agent (ethylene oxide/propylene oxidecopolymer,  8% based on a C13/C15 alcohol, for example Synperonic ™LF/30, ex Croda) Solvent (methanol) 50%

Experimental

Physical Properties and Thermal Stability

A) The physical properties of the demulsifiers 1-4 were tested. Theresults and standard testing methods are detailed in Table 1 below.

TABLE 1 Physical properties Viscosity Cloud 25° C. Density 25° C. Point° C. pH 1% mPa · s (cP) (g/cm³) 5% sample Pour Sample RelativeBrookfield Using a in 35% Point ° C. Solubility in 85:15 SolubilitySpindle measuring BDG: 65% Pour Point 1% Sample in IPA:DI NumberDemulsifier Appearance 29 cylinder DI Water Analyser DI Water Water(RSN) 1 Pale waxy 970 1.0552 +82 +24 Insoluble 6.1 16 solid 2 Amber 13301.092 +60 −9.0 Soluble 7.0 17 liquid 3 Opaque 1140 1.0853 Cloudy +18.0Insoluble 7.2 9 amber liquid 4 Yellow 2260 1.0349 >90 −3.0 Soluble 6.919 clear liquid

B) The thermal stability of the demulsifiers was then tested in air. Thetests were performed at 150° C. and 200° C. The experimental method wasas follows.

Thermogravimetric Analysis (TGA) at 150° C. over 1 hour

-   -   Between 10 and 15 mg of the sample to be tested was weighed into        a    -   70 μL alumina crucible put into the thermogravimetric analyser's    -   (Mettler TG50) furnace and run under air at the following        conditions:    -   Gas (flow rate): Air (200 ml/min)    -   Temperature range:    -   30-150° C. at 50° C./min then    -   150° C. for one hour then    -   150-600° C. at 50° C./min then    -   600° C. for five minutes.

TGA Analysis at 200° C. over 1 hour

-   -   The method as described above was performed, but over the below        temperature range:    -   30-200° C. at 50° C./min then    -   200° C. for one hour then    -   200-600° C. at 50° C./min then    -   600° C. for five minutes.

The percentage mass lost was calculated by step horizontal analysisusing STARe software (version 9.2) on the results of the two methodsdescribed above. The results are shown in Table 2 below.

TABLE 2 Mass loss results Mass lost at Mass lost at Demulsifier 150° C.(%) 200° C. (%) 1 6.6 55.7 2 4.5 70.1 3 2.7 50.5 4 2.9 43.6

Toxicity and Biodegradation

The biodegradation of the demulsifiers was tested according to theguidelines set out in OECD 306 “Biodegradability in Sea Water” (Adopted:17.07.92). The method set out on pages 10 to 17 of the guidelines, i.e.the closed bottle method, was performed. The results are given in Table3 below.

The toxicity of the demulsifiers was tested according to ISO 10253(Second edition, 15.04.2006). The results are given in Table 3 below.

TABLE 3 Toxicity and Biodegradation Results Demulsifier Toxicity (mg/l)Biodegradation (%) 1 238 32 2 47 43 3 648 47 4 5008 11

From the results it can be seen that all of the demulsifiers have lowtoxicity and good biodegradation properties.

Efficacy Tests

Samples of crude oil used was classified using the American PetroleumInstitute (API) test guidelines. The oil was obtained from a UK onshoresource at Star Energy located near to Lincoln in April 2011. The crudeoil samples were cut with water at the percentages described below inTable 4.

TABLE 4 Crude Oil Water Cut Water Cut (%) API (°) Crude Oil Type 10 14.4Heavy 30 15.9 Heavy 50 11.4 Heavy 70 11.4 Heavy

Tests were performed on the oil samples from Table 4 to determine theeffectiveness of the Demulsifiers described above. The tests werecarried out using a TurbiScan TLab Thermo manufactured by Formulaction.The demulsifiers were added to the crude oil at a concentration of 100ppm (in xylene) and analysed in the TurbiScan at 1 scan per minute for60 minutes. The temperature of the TurbiScan was 60° C.

The TurbiScan monitors the duration of the demulsification, along withthe transmission level and clarity of the resulting water phase and thequality of the interface between the resulting water and oil phases.

The results of the TurbiScan tests are given in Table 5.

TABLE 5 TurbiScan test results Crude Oil Time Time Transmission WaterCut Demulsification Demulsification Water Level Demulsifier (%) Started(minutes) finished (minutes) Out (%) (%) Water Clarity Interface Quality1 10 8 30 55 >80 Very Excellent clear 1 30 34 >60 55 >80 Very Excellentclear 1 50 32 55 55 >80 Very Excellent clear 1 70 4 12 68 >60 AverageExcellent 2 10 10 50 52 >80 Very Excellent clear 2 30 31 >60 40 >80 VeryExcellent clear 2 50 29 50 49 >80 Very Excellent clear 2 70 6 50 66 >70Clear Excellent 3 10 8 20 56 ≈40 Poor Average 3 30 8 20 59 ≈50 Average/Average Poor 3 50 8 35 56 ≈60 Average Average 3 70 2 50 62 ≈30 Poor/Average cloudy 4 10 6 >60 33 >80 Very Excellent clear 4 30 44 >60 7 >80Very Excellent clear 4 50 29 >60 31 >80 Very Excellent clear 4 70 3 5558 >70 Clear Excellent

The present invention, therefore, provides a demulsifier which shows thesame or superior properties and efficacy as the standard productionchemicals, but which is environmentally friendly and reaches orsurpasses the rules of the OSPAR.

The demulsifier of the present invention shows good stability, so it caneasily be stored onsite at off-shore drilling locations until requiredfor use. When used, the demulsifier shows good efficacy in demulsifyingcrude oil emulsions, and has superior biodegradability and toxicityproperties meaning it can safely be discharged into the sea/oceanwithout further treatment of the aqueous phase of the demulsifiedemulsion being required.

Any or all of the disclosed features, and/or any or all of the steps ofany method or process described, may be combined in any combination.

Each feature disclosed herein may be replaced by alternative featuresserving the same, equivalent or similar purpose. Therefore, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The above statements apply unless expressly stated otherwise. The termspecification, for these purposes, includes the description and anyaccompanying claims, abstract and drawings.

1. A demulsifier comprising the reaction product of: a) an alkoxylatedpolyol or ester thereof; and b) a dicarboxylic acid.
 2. (canceled) 3.The demulsifier according to either claim 1, wherein the demulsifier isoperable to separate oil-in-water and/or water-in-oil emulsions.
 4. Thedemulsifier according to claim 1, wherein the polyol in the alkoxylatedpolyol comprises at least 3 hydroxyl groups.
 5. The demulsifieraccording to claim 1, wherein the polyol in the alkoxylated polyol hasthe general formula (Ia):HOH₂C—(CHOH)_(p)—CH₂OH   (Ia) where p is from 1 to
 6. 6. The demulsifieraccording to claim 1, wherein the alkoxylated polyol comprises residuesof a univalent radical R²—O—, or anion R²—O⁻, where R² is an alkylgroup.
 7. The demulsifier according to claim 1, wherein the alkoxylatedpolyol or ester thereof comprises between 1 and 500 alkylene oxideequivalents per molecule.
 8. The novel demulsifier according to claim 1,wherein the dicarboxylic acid is of the formula (IV):HOOC—R³—COOH   (IV) where R³ is a C₂ to C₃₆ hydrocarbyl group which issaturated or unsaturated, linear or branched, and aromatic or aliphatic,and cyclic or non-cyclic.
 9. The novel demulsifier according to claim 1,wherein the molar ratio of alkoxylated polyol or ester thereof todicarboxylic acid in the reaction product is at least 0.05:1 and up to20:1.
 10. The novel demulsifier according to claim 1, wherein thereaction product of the alkoxylated polyol or ester thereof and thedicarboxylic acid further comprises an end-cap.
 11. The demulsifieraccording to claim 10, wherein the end-cap comprises a monocarboxylicacid.
 12. The demulsifier according to either claim 10, wherein themolar ratio of the end-cap to the reaction product of the alkoxylatedpolyol or ester thereof and the dicarboxylic acid is at least 0.05:1 andup to 20:1.
 13. The novel demulsifier according to claim 10, wherein themolar ratio of the alkoxylated polyol or ester thereof to thedicarboxylic acid to the end-cap is at least 1:0.1:1 and up to 1:1:5.14. A demulsification formulation comprising a demulsifier which is thereaction product of: a) an alkoxylated sorbitol or sorbitan ester; b) adicarboxylic acid; and c) optionally, an end-cap.
 15. A method ofdemulsifying an oil-in-water or water-in-oil emulsion, the methodcomprising adding a reaction product of: a) an alkoxylated sorbitol orsorbitan ester; b) a dicarboxylic acid; and c) optionally, an end-cap tothe emulsion.
 16. (canceled)
 17. A method for obtaining a demulsifier,comprising reacting: a) an alkoxylated polyol or ester thereof; with b)a dicarboxylic acid.